LV DC/MV AC Power Conversion Interface Based on Asymmetrical Multilevel Converters

The paper proposes a power conversion stage for interfacing LV DC grids with the MV AC network. The system can incorporate distributed PV generation and battery energy storage through a double-stage architecture based on a sole DC/AC converter operating as an Active Front End (AFE) and distributed isolated DC/DC converters connected to several PV sources. The considered AFE converter is an asymmetrical multilevel converter. Two alternative 15 level and 31 level topologies are examined respectively. The DC/DC power conversion stage is based on SiC Dual Active Bridge (DAB) converters with different transformer turns ratios designed to be coupled with the different AFE DC inputs. Advantages and disadvantages are discussed. Efficiency and power quality performances are analyzed. The results of the proposed overall architectures are compared with the results related to a symmetrical double-stage power conversion system based on DABs and a Cascaded H-Bridge (CHB) converter.